However, in the method used in the prior art, a large quantity of division templates need to be stored, which occupies more storage space, thereby increasing a burden on an encoding and decoding system.
Nowadays, mobile phones and other portable devices are typically equipped with cameras. Normally, the auto-focus is considered to be one of the major weaknesses of such cameras installed in mobile devices, in particular because of its slow speed. Depending on the quality of the image sensor of the camera of the mobile device, the auto-focus may require up to several seconds to properly focus on an object of interest. This rather long time period significantly hampers the user experience, particularly because regularly out-of-focus pictures are obtained, further caused by the need to acquire images when the auto-focus is not completed yet.
The auto-focus of a camera of a mobile phone or portable device is typically configured to be always active, and to attempt a maximization of the sharpness of a camera image or of a particular salient region in the camera image.
A salient region is an area within an image, which depicts content deemed of most interest to the user. Typically, the salient region to focus on can be identified automatically by the device, or can be defined manually by the user. The focusing process of the auto-focus is typically terminated, when sharpness of a salient region is above a threshold or when the user shoots a picture (i.e. presses a dedicated “shutter release button”, which may be realized by operating any button or using a touch screen of the mobile device)